The proposed project represents an investigation of two types of output constraints operating in children's early phonology: (1) those that pertain to the properties of the word itself, the focus of Experimment 1, and (2) those that pertain to the properties of the word in relation to other words, the concern of Experiment 2. In each experiment, two types of solutions to these constraints are examined: (1) children's application of phonological rules that satisfy the output constraints, and (2) their avoidance of the words altogether. For each experiment, novel, individually-selected words and their referents are introduced to the child during play activities and the child's acquisition of these words is carefully monitored. The experimental questions deal with the substantiation of avoidance and its proper characterization in the child's phonological system, the conditions under which idiosyncratic rather than common phonological rules will be adopted by children, the range of speech parameters that children can manipulate/contrast in their idiosyncratic rules, and the nature and possible bases of these rules. To permit a more thorough examination of these issues, speech-language delayed children with age-appropriate neuromotor ability, as well as younger normal children will participate in the experiments.